Greetings from So Cal.I've never heard of a "DO" lens. Could you explain what it is and its purpose?Thank you,Ed

"DO" stands for "Diffractive Optics". Canon use it as a method to make lenses smaller and lighter. They currently offer two "Green ring" lenses: the EF 400mm f/4 DO IS USM ($6,469 list), and the 70-300 f/4.5-5.6 DO IS USM ($1,399).

Smaller diameter, shorter length, and no fluorite crystal, and less manufacturing difficulties using aspherical and diffractive elements instead. The obvious goal is to produce a lens that is smaller and more affordable than todays super high priced big white lenses, but expect that they will be in the 3500-5000 range at least.

I could certainly go for a small 500mm f/5.6 telephoto if I could afford it.

Here are a couple of excerpts of the translated wording. (I believe the word sheets refers to lens elements)

"EFFECT OF THE INVENTION

[Effect of the Invention] [0012] according to the present invention -- manufacture -- an easy, small, and lightweight optical system and imaging device can be provided. "

"It is preferable that the diffraction optical element DOE which has at least 1 diffracted-light faculty D is provided by the 1st lens group L1. By providing the diffraction optical element DOE, it becomes easy to correct a chromatic aberration, without increasing lens number of sheets, and even if it does not use anomalous dispersion glass, such as fluorite whose specific gravity is comparatively heavy, correction of a chromatic aberration is attained. At this time, since the further weight saving can be attained, it is preferable. "

I owned the 70-300 DO lens for a couple of years. While it wasn't a bad lens, the DO did take a bit of a toll on IQ, particularly in situations where lens flare was likely (strong light source striking the front element). Bokeh was a little awkward/choppy at times also. I understand that the 400/4 DO is a very good lens.

I'd like to see a refinement in the DO design that would produce an even better optical quality. The light weight and relatively small package makes a strong selling point for this technology.

I owned the 70-300 DO lens for a couple of years. While it wasn't a bad lens, the DO did take a bit of a toll on IQ, particularly in situations where lens flare was likely (strong light source striking the front element). Bokeh was a little awkward/choppy at times also. I understand that the 400/4 DO is a very good lens.

I'd like to see a refinement in the DO design that would produce an even better optical quality. The light weight and relatively small package makes a strong selling point for this technology.

Canon has a number of recent patents for new DO lens technology, but it seems to be exceedingly difficult to manufacture. It is based on small particles immersed in a resin compound. The resultant radial dispersion of particles can produce a superior lens element that varies its properties radially. The issue is getting the spacing of the particles right in a consistent way, and that may never happen. You can't just pour a powder in a vat of resin and mold a bunch of identical lens elements. Every one will be different.

They did not specifically mention this technology in the patent, but did talk about a resin compound, so its in there somewhere.

I owned the 70-300 DO lens for a couple of years. While it wasn't a bad lens, the DO did take a bit of a toll on IQ, particularly in situations where lens flare was likely (strong light source striking the front element). Bokeh was a little awkward/choppy at times also. I understand that the 400/4 DO is a very good lens.

I'd like to see a refinement in the DO design that would produce an even better optical quality. The light weight and relatively small package makes a strong selling point for this technology.

Canon has a number of recent patents for new DO lens technology, but it seems to be exceedingly difficult to manufacture. It is based on small particles immersed in a resin compound. The resultant radial dispersion of particles can produce a superior lens element that varies its properties radially. The issue is getting the spacing of the particles right in a consistent way, and that may never happen. You can't just pour a powder in a vat of resin and mold a bunch of identical lens elements. Every one will be different.

They did not specifically mention this technology in the patent, but did talk about a resin compound, so its in there somewhere.

It may not be as easy as simply mixing "power" with resin an getting ideal results every time...but I would be willing to bet they could mix lightly charged particles with slightly varying charges in resin, and before it cools use a magnetic or electromagnetic field to disperse them properly.

I owned the 70-300 DO lens for a couple of years. While it wasn't a bad lens, the DO did take a bit of a toll on IQ, particularly in situations where lens flare was likely (strong light source striking the front element). Bokeh was a little awkward/choppy at times also. I understand that the 400/4 DO is a very good lens.

I'd like to see a refinement in the DO design that would produce an even better optical quality. The light weight and relatively small package makes a strong selling point for this technology.

Canon has a number of recent patents for new DO lens technology, but it seems to be exceedingly difficult to manufacture. It is based on small particles immersed in a resin compound. The resultant radial dispersion of particles can produce a superior lens element that varies its properties radially. The issue is getting the spacing of the particles right in a consistent way, and that may never happen. You can't just pour a powder in a vat of resin and mold a bunch of identical lens elements. Every one will be different.

They did not specifically mention this technology in the patent, but did talk about a resin compound, so its in there somewhere.

It may not be as easy as simply mixing "power" with resin an getting ideal results every time...but I would be willing to bet they could mix lightly charged particles with slightly varying charges in resin, and before it cools use a magnetic or electromagnetic field to disperse them properly.

Actually, Canon does give some information about their process in the patents for the diffractive lens.I do not think that the particles are magnetic.

"DESCRIPTION OF THE EMBODIMENTS

[0022] This embodiment provides an optical system with a radial gradient-index optical element having a refractive index that changes in a direction perpendicular to an optical axis in a medium. In comparison with an axial gradient-index optical element having a refractive index that changes in an optical axis direction in the medium, the medium of the radial gradient-index optical element has a refractive power caused by refractive index distribution, So the radial gradient-index optical element has an advantage of correcting the chromatic aberration by setting a proper refractive index distribution.

[0023] In the gradient-index optical element, when a refractive index distribution for each wavelength can be independently controlled, the chromatic aberrations for the d-line, the C-line, the F-line, and the g-line can be simultaneously corrected. However, it is difficult to independently control a refractive index distribution for each wavelength when the gradient-index optical element is actually produced.

[0024] Accordingly, this embodiment properly controls a wavelength dispersion characteristic of the gradient-index optical element, and thereby realizes an optical element that has an effect of correcting the chromatic aberration.

[0025] An ion exchange method, a sol-gel method, and three-dimensional printing are known as a manufacturing method of a gradient-index optical element. These methods can distribute a refractive index by gradually changing a composition ratio of the gradient-index optical element for each location. In this gradient-index optical element, this embodiment properly sets a refractive index distribution so that the following conditional expressions can be satisfied, and the chromatic aberrations for four wavelengths can be well corrected. "

However, as with all patents, its easier said than done, so I'm not overly optimistic about seeing a low cost DO implementation soon.

However, as with all patents, its easier said than done, so I'm not overly optimistic about seeing a low cost DO implementation soon.

Very true...however the entire optical engineering world told Canon that making a viable diffractive grating lens was impossible, and yet, Canon persisted and eventually succeeded. ;P I suspect Canon will figure out a way to make a diffractive particle dispersion lens at some point as well...or something else sufficiently superior to their grating lenses as to solve the IQ problems, and still support the construction of smaller, lighter weight lenses for long focal lengths. Canon is nothing if not persistent.